Treatment of petroleum distillates with an alkali and an aldehyde



Patented Nov.- 4, 1952 UNITED STATES; PATENT OFFICE 2,616,832 j I I 'fTR-EATMENT or PETROLEUM DISTILLATES WITH AN AND AN ALDEHYDE John G. Browder, lliouston, and Alvin Smith, I Baytown, Tex., assignors, by mesne 'assignments, to Standard Oil Development Company,

Elizabeth, N. J 'a corporation of Delaware No Drawing. Application October 14, 1949,

Serialblo. 121,446 r The present invention is directed to a method,

for treating sour petroleum distillates. More particularly, the invention is directed to g the} 6 Claims. (01. 196-29) sweetening of sour; petroleum distillates in, the

presence of an alkali metal hydroxide and a mild oxidizing agent."

Prior to the present invention, it has bee known to treat sour petroleum distillates with aqueous alkaline; solutions, such as solutions er alkali metal hydroxide, to remove hydrogen sul='-' fide and other acidic bodies, following which the sour distillates were treated with sodium plumbite solutionto convert "deleterious sulfur compoundsto compounds which are largely'innocuou's. This and other prior art processes relied on the addi tion of sulfur to; cause the conversion of the} sulfur compounds from mercaptans to 'disulfidesL- Other processes convert the undesirable com pounds by means of lead sulfide, which is then separated from the gasoline. Frequently, the

separation of lead sulfide from the gasoline was not complete, and, consequently, some was car-1 ried over into, storage, which was disadvantageous.

level of the gasoline since it .iswell known that sulfur and is compounds ,afiect gasoline detri-;

mentally.

Efforts have remedy this situation, andthe workers the Furthermore, the addition of sulfur. to, gasoline frequently impaired the octane number been made the prior field have turnedtoadding certain compounds-,;-;

such as phenols and amines, to alkaline solutions, such as sodium; hydroxide, to cause conversion throu h an Qli fili p mechanism of; the dele quently such expedients are unsatisfactory innot solutions of sodium hydroxide which have beenemployed in extraction of mercaptans from sour stock-s. In such a process the ketone is employed to prevent solidification of. sodium hy droxide but such art is silenton employing the ketones in the presence of a mild oxidizing agent foo It has also been known to employ aldehydes in a similar manner.

From the foregoing discussion of the prior art, it will be seen that the petroleum refining industry has been faced with a problem of converting deleterious sulfur compounds present in petroleum distillates to those which do not detrimentally affect the quality of the product.

It is, therefore, the main object of the present invention to provide a treating process in which improved results are obtained in converting objectionable sulfur compounds to harmless bodies.

Another object of the present invention is to provide an improved sweetening. process in which any active material is added to the petroleum distillate being sweetened to catalyze'the conver-,

sion of deleterious sulfur compounds.-

Another object of the present invention is, to provide an improved sweetening process in which small amounts of catalytic reagents are employed.

In the foregoing discussion of the prior art it will be seen that the prior art workers added a. compound such as phenol, amines and ketones to sweetening processes in which alkaline solutions were employed to treat sour naphthas. We have now found that, in distinction to the prior art workers, improved results may be obtained in an oxidative sweetening process in which an alkali metal hydroxide solution is employed by adding in the treating operation catalytic amounts of an organic compound having a ca'r bonyl group such as a ketone or an aldehyde.

Thus, in accordance withthe present invention,

the foregoing objects may be achieved by adding to a mixture of sour petroleum distillate and an alkali metal hydroxide a catalytic amount of an organic carbonyl compound while contacting the sour distillate with very small catalytic quantitles of a solution of alkali metal hydroxide and maintainingin contact therewith a mild oxidizing agent.

Accordingly, the present invention may be. described briefly as involving contacting a'sou'r1 petroleum distillate having a boiling range of; about toabout 750 F. with a'solutionof an alkali metal hydroxide to form afmixture thereof while maintaining in the'mixture a datalytic amount of-carbonyl compoundsuch. as a ketoneor'aldehyde and adding to thermixture undergoing contacting'a mild oxidizill gagent in amount suflicient to sweeten said distillate fol-'- lowing which the alkali metal hydroxide is separated from the contacted distillate.

The carbonyl compound employed in the present invention may be illustrated by the ketones and aldehydes such as acetone, diethylketone, methylethylketone, methyl normal amylketone, dipropyl ketone, dibutyl ketone, dihexyl ketone, dioctyl ketone, and the higher members of the same homologous series. The aldehydes finding employment in the present invention may be illustrated by formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, paraldehyde, and the higher members of the homologous series. Aromatic and cyclic carbonyl compounds are also useful in the practice of the present invention, Thus, methylp-tolylketone, p methylcyclohexanone, benzophenone, acetophenone, benzyl, and the'likemay be used. i

These compounds may be employed in amounts based on the naphtha varying from 0.1 to 1.0 per cent by volume with a preferred range from about 0.5 to 1.0 per cent by volume. It is to be emphasized that the specified amount of carbonyl compound may be added either to the naphtha, to the alkali metal hydroxide solution,

or to the mixture'thereof However, it is to be preferred that the carbonyl compound be added to the naphtha in the case of the aldehyde since there is a tendency to formation of solid bodies when the aldehyde is added to the alkali metal hydroxide.

The alkali metal hydroxide employed in the present invention preferably should be a solution of an alkali metal hydroxide. Preferably the solution should be an aqueous solution having a Baum gravity in the range offrom about 30 to about 50 Baum but solutions of wer st eng h may be ed und r s m nditions. An aqueous solution of sodium hydroxide with a gravity of 40 Baum has been found to give satisfactory results in the practice of the present invention. Other alkali metal hydroxides besides sodium hydroxide may be used, For example, lithium and potassium hydroxides may be used in lieu of sodiumihydroxide but the latter is to be preferred.

The temperature at which the treating operation is conducted will usually be atmospheric m ra u e and may an from b ut 6 R up to 200 F. and sometimes higher temper? atur s m y be em loyed d pen g on the boiling range and the type of the feedstock being treated. A p err em ra range ay be from about 70to abo t 95 F. Satisfa tory results have been obtained at atmospheric teme peratures encountered in the Texas Gulf Coast The present invention will be further illusa y e fo lowing example EXAMPLE I A hydrogen sulfide-free high sulfur petroleum distillate boiling in the kerosene boiling range having a copper number of 40 was divided into 4 oxygen necessary to sweeten the naphtha. The third portion had added to it 0.5% by volume of methylethylketone based on the naphtha and then was contacted with 1% by volume of 50 Baum sodium hydroxide solution in the presence of 300% by volume of the theoretical amount of oxygen required to sweeten. The copper numbers of the three treated samples were then determined immediately and after 1, 3, 5, and hours settling time. The results of these tests are presented in Table I in which the first column shows the treatment with 50 Baum caustic solution and oxygen. The second column shows the results in which acetone was added to the kerosene, and the third column shows the results when methylethylketone was added to the kerosene.

- Table I:

Percent On No. Reduction: After 20 Hours Saybolt Color oing table that the addition of either acetoneor m th th etone to t e aph e e n reductions in copper number after 20 hours settling time of 87.5%,whereas the color when acetone was used as the catalytic agent was improved f;rom the original color value of 22 to a value of 27; when methylethylketone was added to the naphtha the colorwas substantially unchanged at 2|. These results indicate that the ketones are valuable catalytic agents in an oxidative sweetening process.

EXAMPLE. II

In order to demonstrate further the beneficial aspects of the present invention a hydrogen sulfide-free kerosene, which was a raffinate of a kerosene fraction obtained by solvent extraction with sufur dioxide, was divided into three portions. One portion was contacted with a solution of Baum hydroxide in the presence of oxygen. The second portion had' added to it 0.5% by volume based on the kerosene of methyl normal amyl ketone following-which the kerosene containing the ketone wascontacted with'a solution of 50 Baum sodium hydroxide in the presence of oxygen to sweeten the kerosene. The third portion was contacted with 50 Baum sodium hydroxide, to which had been added 0.5% of methylethylketone, in the presence of oxygen, following which the sodium hydroxide solution containing the ketone was separated. The kerosene resulting from these operations was separated from the sodium hydroxide and was then tested for color and copper number immediately after treatment and after settling for 1, 3, 5, 24, and 48 hours.

sents the results where no ketone was employed, the second column presents the results where the ketone was added to the kerosene, and the third column presents the results where the ketone was added to the sodium hydroxide solution.

The results of these tests are given in Table II in Which'the first column pre- Table II -Z 50-Be.'-Na0li[; Per Cent. 1.0 1.0 1.0 Oxygem'Per Cent Theor t' l .300 300 300 Promoter Methyl-N-AmylKetone Methyl-N-Amyl Ketone Amount of Promoter, Per Cen 0.5 0.5 Copper No. beforeTreat 33 l 33 33 Color before"; +22 +22 +22 Copper No. after Treat:

Immediately Aft 26 33 30 LHour After. 7 20 7 l5 6 3 Hours"After 20 -9.5 5 5Hours'-After' '21 .i 3 24 Hours After 22 5.0 2 48 Hours After 21 Color after 24 Hours I.-. 5 +16 19 1 Different from the other treats in that the promoter is added to the caustic and not to the naptha.

Considering the data in Table II it will be im- Table III mediately apparent that without the ketone 3 present substantially little sweetening occurred 6, Caufici:p9]cent i Lo L0 L0 xygen percen T eoretica 300 300 300 300 even after 48 hours settlin It W111 be further Formalaehydeipercent M apparent that the colorhad been decreased from Para1deh yde,percent. o. 5 22 130 5. When the ketone was added to the 83 40 40 65 40 kerosene the copper number was reduced after Immediately men" 35 35 55 settling 24 hours from 33 to 5 with a color loss of 7 ggg ffig 25 19 3 10 only 6 points, whereas when the ketone was added fiolgurs After... IIIIIII "I; to the sodium hydroxide solution the copper numg gg gf g -m 8 5 2 ber was reduced to 2 after 24 hours settling time gg z- 22 I 2 95 and the color was substantially unchanged M19. y

'I'hus" the results show conclusively that the ketojriemaybe added either tothe kerosene or to "the sodium hydroxide solution with the latter giving slightly improved results.

EXAMPLE III a In this example hydrogen sulfide-freeihigli sulfur kerosene, which was a raffinate resulting from sulfur dioxide extraction of a kerosene fraction, was divided into four parts. One part was contacted with 50 Baum sodium hydroxide solution in the presence of 300% per volume of the theoretical amount of oxygen provided to sweeten. The second portion had added to it 0.5% per volume, based on the kerosene, of formaldehyde and itwas' contacted with 50-Baum sodium hydroxide solution in the presence of 300% by volumeof the theoretical amount of oxygen required to sweeten. The third portion was sweetened with a 50 Baum sodium hydroxide solution to which had been added 0.5% by volume, based on the kerosene, of formaldehyde,'while the fourth portion had added to it 0.5% by volume, based on the kerosene, of paraldehyde and then contacted with a'solution of 50 Baum sodium hydroxide in the presence of 300% by volume of thentheoretical 'amount of oxygen required to sweeten. In each case the sodium hydroxide solution was employed in an amount of 1% by volume of the kerosene. The results of these runs are given in Table III in which the quantities of reagents employed and the results obtained on the treated and untreated kerosenes are presented. Column one of Table III presents data on the treat without the employment of the aldehyde, column two presents the results where formaldehyde was added to the kerosene, column three presents data obtained when formaldehyde was added to the caustic solution, and column four gives the results on thekerosene containifig paraldehyde treated in accordance withthe present invention.

Formaldehyde added to cau'sti treated with the mixture.

The results in Table III show that formaldehyde or paraldehyde are both effective in sweet? 0, then the naphtha ening a high sulfur kerosene by reducing the cop--" per number from 40 down to a value as low as 2 without seriously lowering the Saybolt color thereof. The results also show that the aldehyde may be-added either to the kerosene or to the sodiunihydroxide solution.

Since it has been knownin the prior art that formaldehyde and sodium hydroxide in admix ture are extractive agents for the removal of,

mercaptans, a comparison'was made between the practice of the present invention, where a solution of sodium hydroxide was employed to sweet-- run in accordance with the practice of the prior art oxygen was absent. I In order to show the beneficial aspects of the present invention in a conclusive manner, a hydrogen sulfide-free high sulfur kerosenefwhich wasa raffinate resulting from the sulfurdioxi'de extraction ofa kerosene'fractiomwas dividdin p to four portions. One portion was treated with" 1% of 50 Baum sodium hydroxide solution in the presence of 300% by volume of the theoret- 1ca1 amount of oxygen required'to sweeten. The

second portion had added to it 0.5% by volume, based on the kerosene, of formaldehyde and was contacted with 1 %'by volume of 50 Baum causl tic solution in the presence of 300% by volume of f the theoretical amount of oxygen required to sweeten.

Thepriorart practice was illustrated by a run in which the kerosene had added to "it 0.5% by volume, based on the kerosene, of formaldehydef and was thencontacted' with 1% by-volume" of 50 Baum sodium hydroxide solution in the substantial absence of free oxygen. A comparative run was made where the kerosene was mixed with 1% by volume of sodium hydroxide solution to which has been added 0.5% by volume, based on the kerosene, of formaldehyde. This sweetening was also conducted in the substantial absence of free oxygen.

The results of these runs are presented in Table IV in which the two left hand columns present a comparison between contacting in the presence of oxygen but in the absence of formaldehyde and contacting in the presence of oxygen with formaldehyde in the kerosene, while the data in the two right hand columns illustrate the prior art where formaldehyde is added either to the naphtha or to the sodium hydroxide and the treating operation is conducted in the substantial absence of free oxygen.

Table IV Present Prior Art Invention Extraction in Oxygen the Absence Sweetened of Oxygen 50 B. Caustic, percent 1.0 1.0 1.0 1.0 Oxygen, percent Theoretical 300 300 Formaldehyde, percent. 0.5 0. l0. 5 On No. Before Treat 4O 40 40 40 Cu No. After Treat:

Immediately After 35 35 38 lllour After. 25 19 3 Hours After. 5 Hours After; 25 f- Hours After 20 8 22 Percent Cu N 0. Reduction After 20 Hours 50 80 45 17. 5 ybo t olo 1 Formaldehyde added to caustic and the mixture used to treat the naphtha.

It will be apparent from the data in Table IV that when the present invention is employed and formaldehyde is present in the mixture undergoing treatment a reduction in copper number from 40 to 8 is obtained with an appreciable improvement in color. Comparing the prior art practiee with the present invention, it will be seen that after 20 hours settling time the copper number had not beenappreciably reduced. In fact, the instance where the formaldehyde was added to the kerosene and contacted with sodium hydroxide in the absence of oxygen a lesser reduction .in copper number was obtained than when oxygen and a caustic solution were employed in the absence of the aldehyde. Even less bene- .ficial results were obtained in the absence of oxygen when formaldehyde was added to the sodium hydroxide solution. It maybe concluded, therefore, that in the present invention in which an oxida ion reaction is conducted in the presence of catalytic amounts of sodium hydroxide with formaldehyde in the reaction mixture substantially improved results are obtained over prior art processes where extraction is conducted in the absence of free oxygen.

EXAMPLE v treated kerosene from the sodium hydroxide solution and after settling for 1, 3, 24, and 48 hours. The results of these tests are presented in Table V in which the left hand column gives the results without the acetaldehyde present in the sodium hydroxide and column two shows the effect of acetaldehyde when added to the sodium hydroxide solution. It is noticed that even though the acetaldehyde forms a solid mass. when added to the sodium hydroxide a beneficial result was obtained in that the copper number was reduced from 33 to 1 after 24 hours settling.

Table V 50 B. NaOH, percent 1.0 1.0 Theor. Oxygen, percent Theoretical 300 300 Promoter None Acetaldehyde Amount of Promoter, pereent 0. 5 Copper No. before Treat 33 33 Color,before +22 +22 Copper No. after Treat:

Immediately After- 25 19 1 Hour After 20 8 v3 Hours After 20 4. 5

5 Hours After. 21 3. 0

24 Hours After .22 1.0

48 HoursAfter 21 Color after 24 Hours 5 1 Formed solid mass when added to caustic.

The effectiveness of aromatic carbonyl compounds and cyclic carbonyl compounds was il-. lustrated by treating a hydrogen sulfide-free, high sulfur kerosene which was a rafiinate resulting from the sulfur dioxide extraction ofa kerosene fraction. This rafiinate was divided into three portions. One portion was treated with 1 volume per cent of sodium hydroxide with a gravity of 50 Baum in the presence of 300% of the theoretical oxygen required to sweeten the material; another portion had added to it 0.5 volume per cent methyl-p-tolylketone and was then contacted with 1 volume per cent caustic with a gravity of 50 Baum in the presence of 300% of the theoretical oxygen required to sweeten the material; the third portion had added .to it 0.5 vol me per c n n-methyl-cyclohexanone and was then contacted with. 1% by volume of sodium hydroxide with a gravity of 50 Baum in the presence of 300% of the theoretical oxygen required to sweeten the material. The ,copper numbers of the three portions of contacted raffinate were determined immediately after the separation of the treated rafiinate from thesodium hydroxide solution and also after-settling for 3 and 20 hours.

The results of these tests are presented in Table VI. It is to be observed that both the aromatic and cyclic carbonyls are effective promoters although the cyclic compound is more effective than the aromatic compound. The percentage reduction in copper number is over twice as great when the reactionis catalyzed by the aromatic carbonyl as for the uncatalyzed reaction and over three times as great for the reaction catalyzed by the cyclic carbonyl as for the uncatalyzed reaction.

Tab V This is a wellknown analytical procedure in the petroleum industry. A description of the .method of testmay be found in U. 0. P. Laboratory Test Methods for Petroleum and Its Products, third edition, page H6l,,Universal Oil Products'Co., .Chicago, 1947. This test is a measure of the mercaptansulfur content of the oil being tested.

Although not illustrated by the several examples, one of the particular advantages of the present invention resides in the catalytic efiect of the alkali metal hydroxide solution. The alkali metal hydroxide appears to function as a true catalyst since the small amount used may be recycled to treat large quantities of the sour petroleum distillate. A small amount of the alkali metal hydroxide solution may be entrained in the treated naphtha, and, therefore, it may be necessary to replace the entrained amount with fresh solution. In short, it is contemplated in the practice of the present invention that the alkali metal hydroxide solution will be reused over and over again since it is not necessary to regenerate the alkali metal hydroxide solution.

The invention has been described and illustrated by employement of a mild oxidizing agent such as oxygen. It is contemplated that mixtures of oxygen with other gases, such as air, may be employed. It is also contemplated that other mild oxidizing agents such as peroxides, permanganates, and the like may be used. For example, a hydrogen peroxide solution may be employed as the mild oxidizing agent.

In practicing the present invention, it is to be understood that the petroleum distillate may be subjected to a preliminary treatment for removal of hydrogen sulfide if the distillate contains hydrogen sulfide. Such preliminary treatment may include washing with a dilute alkali metal hydroxide solution or blowing with a free-oxygen containing gas such as air. If hydrogen sulfide or other acidic compounds are present and not removed, the alkali metal hydroxide solution employed as the catalyst may very quickly become seriously depleted in activity.

In the practice of the invention, it will be desirable to use an amount of oxygen in excess of the theoretical required to sweeten the sour petroleum distillate. Ordinarily, an amount of about 300% of the theoretical amount to sweeten may be employed. However, sweetening in accordance with the present invention may be obtained with considerably lesser uantities of oxygen. In other instances as much as 500% of the-theoretical amount required to sweeten may be employed. In fact, sweetening may be obtained in some cases by contact with the oxygen present in the treating vessel. It will be desirable to employ an amount of oxidizing agent at least equivalent to the theoretical amount required to sweeten.

The invention has been described and exemplified by employment of 0.5 to 1.0% by volume of the catalytic alkali metal hydroxide solution. It is contemplated that as little as 0.1 and as much as by volume, or more, of the alkali metal hydroxide solution, based on the sour naphtha, may be employed. Very good results, however, are obtained with 1% by volume and this amount will 'be preferred.

The nature and objects of the present invention having been completely described and illustrated, what ,we'wish to claim as new and useful and to secure by Letters Patentis:v l. A method for treating a petroleum distillate which comprises contacting a sour petroleum distillate containing mercaptans and boiling below 750 F. with a catalytic amount in the range between 0'.1% and 5% by volume based on the distillate of a solution of an alkali metal hydroxide in the presence of less than 1.0% by volume based on the distillate of an "aldehyde while adding a mild oxidizing agent in a suflicient amount to obtain a sweetened distillate.

. 2. A method for sweetening a sour petroleum distillate containing mercaptans and boiling below 750 F. which comprises forming a mixture of an aqueous solution of an alkali metal hydroxide in a catalytic amount in the range between 0.1% and 5% by volume based on the sour distillate and said sour petroleum distillate, maintaining in said mixture an amount of an aldehyde in the range from 0.1 to 1.0% by volume based on said distillate, and then contacting the mixture while and then contacting the mixture while adding a" sufiicient amount of air to obtain a sweetened distillate.

4. A method for sweetening a sour petroleum distillate containing mercaptans and boiling below 750 F. which comprises forming a mixture of an aqueous solution of sodium hydroxide in a catalytic amount in the range between 0.1% and. 5% by volume based on the sour distillate and, said sour petroleum distillate, adding to said mixture an amount of an aldehyde in the range from 0.1 to 1.0% by volume based on said distillate, and then contacting the mixture while adding a sufiicient amount of air for a time sufficient'to cause sweetening of said distillate, separating said sodium hydroxide solution from said distillate, and recovering said agitated distillate.

5. A method for sweetening a sour petroleum distillate containing mercaptans and boiling below 750 F. which comprises forming a mixture of an aqueous solution of sodium hydroxide in a catalytic amount in the range between 0.1% and 5% by volume based on the sour distillate and said sour petroleum distillate, adding to said mixture an amount of an aldehyde in the range from 0.1% to 1% by volume based on said distillate selected from the class consisting of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, and paraldehyde, and then contacting the mixture while adding a suflicient amount of air for a time suificient to cause sweetening of said distillate, separating said sodium hydroxide solution from said contacted distillate and recovering said contacted distillate.

6. A method for sweetening a sour petroleum distillate containing mercaptans and boiling below 750 F. which comprises adding to said distillate an amount of an aldehyde in the range from 0.1% to 1% by volume based on said distillate, and then contacting the distillate to which the aldehyde has been added with an aqueous 11 solution of sodium hydroxide in a catalytic amount in the range between 0.1% and 5% by volume based on the sour distillate while adding a sufficient amount of air for a time sufficien't to cause sweetening of said distillate, separating said sodium hydroxide Solution from said contacted distillate and recovering said contacted distillate.

JOHN G. BROWDER.

ALVIN R. SMITH.

REFERENCES CITED The following references are of record inthe file of this patent:

. 1 umber 12 UNITED STATES PATENTS Name Date Stratford et a1. u- Apr. 17, 1934 Pevere ei Sept. 1'1, 1935 f; 2,015,038 2,043,254 5 2,059,075 2, 23,492 v 2,146,253 2,316,759 2;, 2,345,449 'T 2,464,576

Bond Apr. 20. 1943 Birkhimernheuel- Mar. 28, 1944 Hibbard et a1. Mar. 15. 1949 Bernard Nov. 15, 1949 OTHER REFERENCES 15 Russell, science, pages 372-3, Oct. 17, 1947. 

1. A MEHOD FOR TREATING A PETROLEUM DISTILLATE WHICH COMPRISES CONTACTING A SOUR PETROLEUM DISTILLATE CONTAINING MERCAPTANS AND BOILING BELOW 750* F. WITH A CATALYTIC AMOUNT IN THE RANGE BETWEEN 0.1% AND 5% BY VOLUME BASED O THE DISTILLATE OF A SOLUTION OF AN ALKALI METAL HYDROXIDE IN THE PRESENCE OF LESS THAN 1.0% BY VOLUME BASED ON THE DISTILLATE OF AN ALDEHYDE WHILE ADDING A MILD OXIDIZING AGENT IN A SUFFICIENT AMOUNT TO OBTAIN A SWEETENED DISTILLATE. 